Processor performance state optimization

ABSTRACT

A processor performance state optimization includes a system to change a performance state of a processor. In an embodiment, the system to change a performance state of the processor includes a processor and a step logic sub-system operatively coupled with the processor and is operable to communicate a performance state change request to the processor. A core voltage regulator is operatively coupled with the step logic sub-system. An end performance state sub-system to determine a desired end performance state is coupled with the step logic sub-system. And, an enable sub-state transition sub-system to enable sub-state transitions is coupled with the step logic sub-system.

BACKGROUND

The present disclosure relates generally to information handling systems(IHSs), and more particularly to IHS processor performance stateoptimization.

As the value and use of information continues to increase, individualsand businesses seek additional ways to process and store information.One option is an information handling system (IHS). An IHS generallyprocesses, compiles, stores, and/or communicates information or data forbusiness, personal, or other purposes. Because technology andinformation handling needs and requirements may vary between differentapplications, IHSs may also vary regarding what information is handled,how the information is handled, how much information is processed,stored, or communicated, and how quickly and efficiently the informationmay be processed, stored, or communicated. The variations in IHSs allowfor IHSs to be general or configured for a specific user or specific usesuch as financial transaction processing, airline reservations,enterprise data storage, or global communications. In addition, IHSs mayinclude a variety of hardware and software components that may beconfigured to process, store, and communicate information and mayinclude one or more computer systems, data storage systems, andnetworking systems.

IHSs are generally understood in the art to operate using a processor toprocess information. Current processor control algorithms have beenfound through experimentation when running bursty applications to givehigher performance and lower power consumption when using minimum andmaximum performance states and transitioning between the two. Aprocessor may process information by running as fast as possible to geta piece of work done and then sleeping the system until the nextprocessing information arrives. Traditionally, processors begin runningat a lowest performance state and let the voltage continue to slew to avoltage required by the intended performance state and then transitionthe operating frequency once this occurs. However, with a processorhaving many performance states, the processor spends a large amount oftime at the lowest speed with much higher voltages than required for thegiven operating frequency. This results in a power penalty for theperformance of the processor obtained at the low operating frequency.

Accordingly, it would be desirable to provide improved processorperformance state optimization absent the deficiencies described above.

SUMMARY

According to one embodiment, a system to change a performance state of aprocessor includes a processor and a step logic sub-system operativelycoupled with the processor and is operable to communicate a performancestate change request to the processor. A core voltage regulator isoperatively coupled with the step logic sub-system. An end performancestate sub-system to determine a desired end performance state is coupledwith the step logic sub-system. And, an enable sub-state transitionsub-system to enable sub-state transitions is coupled with the steplogic sub-system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an embodiment of an information handling system(IHS).

FIG. 2 illustrates a prior art embodiment of a processor performancestate change method.

FIG. 3 illustrates an embodiment of an optimized processor performancestate change method.

FIG. 4 illustrates a logic block diagram for an embodiment of a substate change system internal to processor.

FIG. 5 illustrates a logic block diagram for an embodiment of a substate change system external to processor.

FIG. 6 illustrates an embodiment of a transition diagram showing workpotential between performance states.

DETAILED DESCRIPTION

For purposes of this disclosure, an IHS 100 includes any instrumentalityor aggregate of instrumentalities operable to compute, classify,process, transmit, receive, retrieve, originate, switch, store, display,manifest, detect, record, reproduce, handle, or utilize any form ofinformation, intelligence, or data for business, scientific, control, orother purposes. For example, an IHS 100 may be a personal computer, anetwork storage device, or any other suitable device and may vary insize, shape, performance, functionality, and price. The IHS 100 mayinclude random access memory (RAM), one or more processing resourcessuch as a central processing unit (CPU) or hardware or software controllogic, read only memory (ROM), and/or other types of nonvolatile memory.Additional components of the IHS 100 may include one or more diskdrives, one or more network ports for communicating with externaldevices as well as various input and output (I/O) devices, such as akeyboard, a mouse, and a video display. The IHS 100 may also include oneor more buses operable to transmit communications between the varioushardware components.

FIG. 1 is a block diagram of one IHS 100. The IHS 100 includes aprocessor 102 such as an Intel Pentium™ series processor or any otherprocessor available. A memory I/O hub chipset 104 (comprising one ormore integrated circuits) connects to processor 102 over a front-sidebus 106. Memory I/O hub 104 provides the processor 102 with access to avariety of resources. Main memory 108 connects to memory I/O hub 104over a memory or data bus. A graphics processor 110 also connects tomemory I/O hub 104, allowing the graphics processor to communicate,e.g., with processor 102 and main memory 108. Graphics processor 110, inturn, provides display signals to a display device 112.

Other resources can also be coupled to the system through the memory I/Ohub 104 using a data bus, including an optical drive 114 or otherremovable-media drive, one or more hard disk drives 116, one or morenetwork interfaces 118, one or more Universal Serial Bus (USB) ports120, and a super I/O controller 122 to provide access to user inputdevices 124, etc. The IHS 100 may also include a solid state drive(SSDs) 126 in place of, or in addition to main memory 108, the opticaldrive 114, and/or a hard disk drive 116. It is understood that any orall of the drive devices 114, 116, and 126 may be located locally withthe IHS 100, located remotely from the IHS 100, and/or they may bevirtual with respect to the IHS 100.

Not all IHSs 100 include each of the components shown in FIG. 1, andother components not shown may exist. Furthermore, some components shownas separate may exist in an integrated package or be integrated in acommon integrated circuit with other components, for example, theprocessor 102 and the memory I/O hub 104 can be combined together. Ascan be appreciated, many systems are expandable, and include or caninclude a variety of components, including redundant or parallelresources.

The advanced configuration and power interface (ACPI) performance statesare commonly used as processor 102 and other device performancestandards and are commonly understood by those having ordinary skill inthe art. ACPI specification is an open industry standard that definescommon interfaces for hardware recognition, motherboard and deviceconfiguration and power management. Using ACPI, an operating system (OS)for an IHS is generally in control of the power management of the IHS.As is also commonly understood by those having ordinary skill in theart, processor 102 power states are generally know as C0 (operatingstate), C1 (halt), C2 (stop-clock), and C3 (sleep). Performance statesfor the processor 102 and other devices are generallyimplementation-dependent, where P0 is the highest performance state,with P1 to Pn being successively lower-performance states. Powerconsumption in semiconductor type devices equals a switching function(Voltage²·frequency·capacitance·constant) plus a leakage function(Voltage²/Resistance). Therefore, it follows that changing both voltageand frequency of operation for the processor yields exponential changesin power consumption for the device (e.g., a processor 102). It isgenerally understood that there is a minimum operating frequency for thesemiconductor device for a given voltage.

FIG. 2 illustrates a prior art embodiment of a processor 102 performancestate change method 130. The method 130 begins at block 132 where theprocessor is presently in one of several available performance states.The method 130 proceeds to decision block 132 where the method 130determines whether a time since the last processor 102 calculationequals a pre-determined time delay. If no, the time since the lastprocessor 102 calculation does not equal a pre-determined time delay,the method 130 returns to block 132. If yes, the time since the lastprocessor 102 calculation does equal a pre-determined time delay, themethod 130 proceeds to block 136 where the method 130 collects data andcalculates processor business for the interval time since the lastcalculation. The method 130 then proceeds to decision block 138 wherethe method 130 determines whether a performance state change isrequired. If no, no performance state change is required, the method 130returns to block 132. If yes, a performance state change is required,the method 130 proceeds to block 140 where the method 130 changes theperformance state of the processor 102. The method 130 then returns toblock 132 and starts over.

FIG. 3 illustrates an embodiment of an optimized processor performancestate change method 144. The method 144 begins at block 146 where theprocessor 102 is presently in one of several available performancestates. The method 144 proceeds to decision block 148 where the method144 determines whether a time since the last processor 102 calculationequals a pre-determined time delay. If no, the time since the lastprocessor 102 calculation does not equal a pre-determined time delay,the method 144 returns to block 146. If yes, the time since the lastprocessor 102 calculation does equal a pre-determined time delay, themethod 144 proceeds to block 150 where the method 144 collects data andcalculates processor business for the interval time since the lastcalculation. The method 144 then proceeds to decision block 152 wherethe method 144 determines whether a performance state change isrequired. If no, no performance state change is required, the method 144returns to block 146. If yes, a performance state change is required,the method 144 proceeds to block 154 where the method 144 changes theperformance state of the processor 102. The method 144 then proceeds todecision block 156 where the method 144 determines whether intermediatestepping of voltage and/or frequency between pre-determined performancestates levels is required. If no, the method 144 returns to block 146.If yes, intermediate stepping is required, the method 144 proceeds toblock 158 where the method 144 sets a sub-step timer. The method 144then proceeds to decision block 160 where the method 144 determineswhether the sub-step timer has expired. If no, the method 144 returns todecision block 160. If yes, the sub-step timer has expired, the method144 proceeds to block 162 where the method 144 sends a processor statechange request. The method 144 then proceeds to decision block 164 wherethe method 144 determines whether the desired performance state has beenachieved. If no, the method 144 returns to block 158. If yes, thedesired performance state has been achieved, the method returns to block146 and starts over.

FIG. 4 illustrates a logic block diagram for an embodiment of a substate change system 170 internal to the processor 102. In this system170, the processor 102 includes a step logic system 172 for reviewing apre-loaded performance ramp table and determining when performance statechanges and performance sub-state changes are desirable and initiatingsuch changes. The step logic system 172 communicates a voltageidentification 174 to a core voltage regulator 176. Therefore, the steplogic system 172 informs the core voltage regulator 176 of the desiredvoltage for the processor 102 core. When informed of the desired voltagelevel for the processor 102 core, the core voltage regulator 176 mayregulate the processor 102 core operating voltage. It is generallyunderstood that changing the core voltage level requires a slew time forthe voltage to change to a new desired level. Therefore, changing avoltage level may be performed before changing a frequency level whenchanging performance states allowing the voltage to sloop to the desiredlevel before the frequency is changed. This keeps the processor 102operating above a minimum core voltage operating level.

FIG. 5 illustrates a logic block diagram for an embodiment of a substate change system 180 external to processor 102. In this system 180,the processor 102 couples with an external step logic system 182 forreviewing a pre-loaded performance ramp table and determining whenperformance state changes and performance sub-state changes aredesirable and initiating such changes. The step logic system 182receives a voltage identification 184 from the processor. The step logicsystem 182 communicates a voltage identification 186 to a core voltageregulator 188. Therefore, the step logic system 182 informs the corevoltage regulator 188 of the desired voltage for the processor 102 core.When informed of the desired voltage level for the processor 102 core,the core voltage regulator 188 may regulate the processor 102 coreoperating voltage. The step logic 182 receives a desired end performancestate input 190 informing the step logic 182 of a desired endperformance state for the processor 102. The step logic 182 may use thedesired end performance state input 190 to determine how to performintermediate steps for voltage and/or frequency between definedperformance states. The step logic 182 also receives an enable sub statetransition input informing the step logic 182 if sub state transitionsare available for the processor 102. The step logic 182 uses the voltageidentification input 184, the desired end performance state input 190,and/or the enable sub state transitions input 192 to determine if andhow intermediate steps should be taken in voltage and/or frequencybetween the performance states and communicates outputs of a voltageidentification 186 and a performance state change request 194 to thecore voltage regulator 188 and the processor 102 respectively.

FIG. 6 illustrates an embodiment of a transition diagram 200 showingwork potential between performance states along a processor 102 coreoperating level 202. An existing performance state Pn 204 is shown. Adesired or target performance state P0 206 is also shown. This diagram200 shows that one or more work potential states Pn-1 208, Pn-2 210exist between the performance states 204, 206 along the operating level202.

Referring to FIGS. 4, 5, and 6, both of the systems 170, 180 should beinitialized with a set of voltages for supported performance states.During transition from one performance state to another performancestate, the systems 170, 180 would know a desired final performancestate. Combining this knowledge with a preloaded supported performancestate table would allow the systems 170, 180 to initiate sub-statechanges along the ramp 202.

In an embodiment, when transitioning up in voltage, the system 170, 180would compare a present voltage to a voltage required for all supportedperformance states with higher voltage requirements than the presentperformance state. Then, the system 170, 180 would initiate a processorperformance state change when the present voltage is greater than orequal to the next supported performance state voltage as defined onperformance state table.

In an embodiment, when transitioning down in voltage, the system 170,180 may transition by determining when present voltage is substantiallyequal to a present performance state minimum voltage plus a presetoffset voltage and when so, initiating a transition to a next lowervoltage performance state. The offset assures that transition occursbefore voltage gets below a minimum for the present performance state.As such, this allows a voltage reduction to be continuous.

In an embodiment, when transitioning down in voltage, the system 170,180 may transition by reducing voltage to a minimum for the presentperformance state and pause the voltage reduction. Then, the system 170,180 may initiate a performance state change, wait for it to complete andreduce voltage to the minimum for the new performance state.

In an embodiment, a hardware change from present processor architecturesupports transitions to intermediate performance states during rampingof voltage between performance states that have intermediate states.This allows the processor performance to adjust as the voltage slews andgains more performance relative to the higher power dissipation due tothe higher voltage. A similar situation exists on transitions fromhigher performance states to lower ones.

In IHS operating systems software drivers generally perform performancestate changes for the processors 102. However, most operating systems donot change faster than about every 50 msec. A slow part of theperformance state transition is the voltage slew from one value toanother value. To the contrary, frequency changes may take place in afew micro seconds to a few clock cycles. Therefore, it is generallydesirable to slew the voltage first and then tell the controller tochange the frequency. This can be performed in reverse whentransitioning to a lower performance state. In an embodiment, thetransition to intermediate performance states is performed by hardware,such as shown in FIG. 5, because the hardware can react faster thansoftware initiated state changes and thus, improves IHS 100 performance.It is a benefit in both desktop and mobile devices to transition to lowpower as soon as possible to save power. In an embodiment, an operatingpoint may be controlled by the operating system, but during slew times,hardware may be used to ramp the system using intermediate stepsfollowing the slew/frequency level at allowable operating points.

Although illustrative embodiments have been shown and described, a widerange of modification, change and substitution is contemplated in theforegoing disclosure and in some instances, some features of theembodiments may be employed without a corresponding use of otherfeatures. Accordingly, it is appropriate that the appended claims beconstrued broadly and in a manner consistent with the scope of theembodiments disclosed herein.

1. A system for changing performance states of a processor, comprising:a processor; a core voltage regulator coupled to the processor; and astep logic sub-system coupled with the processor, the core voltageregulator, and a performance ramp table, wherein the step logicsubsystem is operable, in response to receiving a desired endperformance state for the processor, to: use the performance ramp tableto determine a plurality of intermediate performance states for theprocessor between a current performance state for the processor and thedesired end performance state for the processor; and determine a minimumvoltage required for each of the plurality of intermediate performancestates with higher voltage requirements than the current performancestate; wherein for each of the plurality of intermediate performancestates, the step logic subsystem is operable to: instruct the corevoltage regulator to provide the minimum voltage for that intermediateperformance state to the processor; and initiate a voltage-increaseperformance state change in the processor when the minimum voltage forthat intermediate performance state is provided to the processor.
 2. Thesystem of claim 1, wherein the step logic sub-system is internal to theprocessor.
 3. The system of claim 1, wherein the step logic sub-systemis external to the processor.
 4. The system of claim 1, wherein theperformance ramp table is pre-defined.
 5. The system of claim 1, whereinthe step logic sub-system is further operable to: compare a currentperformance state voltage to a current performance state minimum voltageplus an offset voltage; and initiate a voltage-decrease performancestate change when the present voltage substantially equals the presentperformance state minimum voltage plus the offset voltage.
 6. The systemof claim 1, wherein the step logic sub-system is further operable to:begin reducing a current performance state voltage; pause reducing thecurrent performance state voltage; initiate a performance state change;wait for the performance state change to complete; and resume reducingthe current performance state voltage.
 7. An information handling system(IHS) comprising: a processor; a memory hub coupled with the processor;and a system to change performance state of the processor, the system tochange performance state of the processor further comprising: a corevoltage regulator coupled to the processor; and a step logic sub-systemcoupled with the processor, the core voltage regulator, and aperformance ramp table, wherein the step logic subsystem is operable, inresponse to receiving a desired end performance state for the processor,to: use the performance ramp table to determine a plurality ofintermediate performance states for the processor between a currentperformance state for the processor and the desired end performancestate for the processor; and determine a minimum voltage required foreach of the plurality of intermediate performance states with highervoltage requirements than the current performance state; wherein foreach of the plurality of intermediate performance states, the step logicsubsystem is operable to: instruct the core voltage regulator to providethe minimum voltage for that intermediate performance state to theprocessor; and initiate a voltage-increase performance state change inthe processor when the minimum voltage for that intermediate performancestate is provided to the processor.
 8. The IHS of claim 7, wherein theperformance map table is pre-defined.
 9. The IHS of claim 7, wherein thestep logic sub-system is internal to the processor.
 10. The IHS of claim7, wherein the step logic sub-system is further operable to: compare acurrent performance state voltage to a current performance state minimumvoltage plus an offset voltage; and initiate a voltage-decreaseperformance state change when the present voltage substantially equalsthe present performance state minimum voltage plus the offset voltage.11. The IHS of claim 7, wherein the step logic sub-system is furtheroperable to: begin reducing a current performance state voltage; apresent performance state and pauses reducing the current performancestate voltage; initiate a performance state change; wait for theperformance state change to complete; and resume reducing the currentperformance state voltage.